This leads to some interesting questions regarding what human intelligence and decision making abilities actually are. How much of our behavior is pre-programmed and how much is up to us?
Naturally, we can act selfishly in a clean environment, but apparently there is impetus to do the opposite, which we must overcome to carry out the selfish act. Is the opposite true in a dirty environment? could we sentence people to clean their house three or more times a week and reduce the number of people in prison? Lots of fun questions to play with here.